Former Boxer Throws Support Behind Businessman Petro Poroshenko

KIEV, Ukraine—Campaigning for Ukraine's presidential elections kicked off in earnest Saturday as the U.S.'s and Russia's top diplomats prepared to meet Sunday to discuss the region's crisis.

The developments come amid mounting tensions about thousands of Russian troops assembling on Ukraine's eastern border, and worries Moscow may try to seize more of that nation's territory after annexing Crimea.